so got some week old fry some look grey in colour others look brown (which i expected) and also looks like one might be a lemon (pic 1) ...mum is lemon dad is brown so wondering where grey would come from or will it go dark brown like rest seem to be already thoughts?

Not sure on pleco genetics but with all breeding there is "3 legs" as I refer to it.
1 is mom ,2 is dad and the third leg is one of mom or dads parents.Some fish also don't breed true and crossing color variations can yield random results.I had a pair of "Red finned " angels that shot every color under the sun except albino and black..For real...
I kept a pair of platinums from them !